I know that Jenny's post was at while ago but just in case others are having the same problems ....... The only problems that I can think of that can affect seedlings are pests, damping off, over-watering, under-watering, windburn, too little light or sunburn. I've just sunburned one of my tomato seelings on the window sill inside the house. :-( If it is not any of the above, Then I have not a clue and maybe a wiser head could give advice! :-)